Known organic super-conductive substances having a critical temperature (Tc) of 10K or higher include cation radical salts having a low molecular weight, such as a Cu(NCS).sub.2 salt of bis(ethylenedithiatetra-thia)fulvalene (hereinafter abbreviated as "BEDT-TTF", the Cu(NCS).sub.2 salt thereof being represented by "(BEDT-TTF).sub.2 Cu(NCS).sub.2 ") (Tc: 10. 4K) and deuterated (BEDT-TTF).sub.2 Cu (NCS).sub.2 ((BEDT-TTFd.sub.8).sub.2 Cu(NCS).sub.2 ; Tc: 11K) as described in H. Urayama et al., Chem. Lett., p. 55 (1988).
(BEDT-TTF).sub.2 Cu(NCS).sub.2 can be obtained by electrochemical oxidation of BEDT-TTF, effected by applying a direct electrical current through a solution of BEDT-TTF in 1, 1, 2-trichloroethane in the presence of CuSCN, KSCN, and 18-crown-6-ether as described in H. Urayama et al., Chem. Lett., p. 55 (1988).
However, it has been difficult to process and shape these conventionally known organic superconductive substances into fibers, films, etc., because of their very fine and brittle crystals. The difficulty of processing has been a bar to sufficient industrialization of organic superconductive substances.